---
id: CVE-2026-57580
title: authentik is an open-source identity provider
summary: >-
  authentik is an open-source identity provider. Prior to 2026.2.6 and 2026.5.5,
  an inbound SAML Source configured with the non-default USERNAME_LINK or
  EMAIL_LINK user-matching mode interprets an XML comment in a NameID
  differently from t…
severity: none
cwe:
  - CWE-436
published: '2026-08-18'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T21:02:26.047'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-57580'
references:
  - url: >-
      https://github.com/goauthentik/authentik/commit/6bd00f09f1f6b5bc5212a10340418fa1b264f02c
    label: security-advisories@github.com
  - url: >-
      https://github.com/goauthentik/authentik/commit/8704a1b89d7bf46bcef0d3c434c821b937fdecc3
    label: security-advisories@github.com
  - url: 'https://github.com/goauthentik/authentik/pull/24057'
    label: security-advisories@github.com
  - url: 'https://github.com/goauthentik/authentik/pull/24062'
    label: security-advisories@github.com
  - url: 'https://github.com/goauthentik/authentik/releases/tag/version/2026.2.6'
    label: security-advisories@github.com
  - url: 'https://github.com/goauthentik/authentik/releases/tag/version/2026.5.5'
    label: security-advisories@github.com
  - url: >-
      https://github.com/goauthentik/authentik/security/advisories/GHSA-35v6-hv2g-6992
    label: security-advisories@github.com
tags:
  - nvd
epss: 0.0059
epssPercentile: 0.45925
ingestedAt: '2026-09-08T21:11:12.282Z'
---

## Overview

authentik is an open-source identity provider. Prior to 2026.2.6 and 2026.5.5, an inbound SAML Source configured with the non-default USERNAME_LINK or EMAIL_LINK user-matching mode interprets an XML comment in a NameID differently from the identity provider's signed assertion. An attacker with an account on the source identity provider who can set the account's NameID can inject an XML comment that truncates the value used by authentik to the text before the comment while the signed assertion remains valid. A crafted NameID can therefore truncate to a victim's username or email and bind the attacker's external identity to the victim's existing account. This grants full takeover without the victim's password or the identity provider's private key, and the malicious link persists so later logins succeed without the comment. Sources using the default unique-identifier matching mode and authentik's outbound SAML Provider role are not affected. This issue is fixed in versions 2026.2.6 and 2026.5.5.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.